1. Field of the Invention
The present invention relates to a three-dimensional computer graphic apparatus having a function to designate a processing order of a plurality of graphic data which are output from a plurality of parallel processing units, for example, processor modules connected in parallel, which are included in the apparatus.
2. Description of the Related Art
In general, in a three-dimensional computer graphic apparatus, it is necessary to carry out the following steps of converting a three-dimensional model (i.e., object) into a two-dimensional image to be displayed on the apparatus. First, a viewpoint and light source are determined on the three-dimensional model. Second, the graphic data are determined from the three-dimensional model in accordance with the viewpoint and light source. Third, geometric conversion is carried out for the graphic data in the apparatus. The geometric conversion includes an ordinate calculation, clipping operation, color density calculation, etc.
Further, after geometric conversion, a predrawing process, for example, a span-generation process, is carried out on the result of each geometric conversion. Finally, after the pre-drawing process, a drawing process, for example, a spanning and an erasing process, is carried out on the result of the pre-drawing process. As a result, the graphic data of the three-dimensional model is converted to a two-dimensional image to be displayed on the apparatus in accordance with the viewpoint.
In this structure, for example, the processor module is used for the geometric conversion and the pre-drawing process, and the processor module is used for the drawing process.
In order to carry out the above processes at high speed, in general, the apparatus includes a plurality of parallel processing units, for example, processor modules connected in parallel. The processor modules are formed of pipeline structures, and the graphic data are sequentially processed in parallel passing through each pipeline.
In the pipeline processing mentioned above, it is impossible to designate a processing order of the graphic data. This is because data from each pipeline are sequentially processed in parallel for every data train. That is, when detecting a break in the data train, a next data train is sequentially processed in parallel for another pipeline without any designation from an operator.
Accordingly, if the operator wishes to designate a processing order of the graphic data, it is necessary to make one pipeline operate, so as to carry out a designation of the processing order, and to temporarily stop other pipeline processing. As a result of the above designation, a problem occurs in that the throughput of the overall apparatus deteriorates.